The concern over protecting medical personnel from coming into contact with infectious diseases by contact with contaminated syringe needles has led to the development of many syringes with retractable needles. The recent concern over the avoidance of being infected with the HIV (or AIDS) virus has led to even a greater importance being placed in the use of syringes incorporating retractable needles.
U.S. Pat. Nos. 4,650,468 and 4,643,199 are examples of syringes which have been developed so as to allow for a potentially infectious needle to be withdrawn into the syringe's interior after use. Both of theses patents utilize a somewhat complex mechanism to position the needle in an operational position and/or to retract the needle back into the syringe housing. The complexity of these designs can be a problem when quick positioning of the needle is essential, e.g., in an emergency situation.
U.S. Pat. Nos. 4,507,117 and 4,675,005 illustrate other syringe designs having retractable needles which are releasably connected directly to the plunger by way of rotation. As above, the complex mechanisms employed by these syringe designs can be a problem when quick positioning of the needle is essential, e.g., in an emergency situation.
U.S. Pat. No. 4,692,156 shows a retractable syringe needle which is locked directly onto the sealing plug of a plunger. In one embodiment, there is disclosed a snapping connection means between the needle and plug. Once this snapping connection has been made, it is essentially nondetachable and thus this invention represents a one shot device. In other words, any inadvertent attachment before use cannot be remedied.
Other syringes having safety features that have been designed to prevent accidental punctures and/or which prevent reuse are shown in the following patents:
U.S. Pat. No. 4,664,653 which describes a one step manually activated injection apparatus capable of injecting multiple premeasured dose of liquid medicaments without visibility of the needle.
U.S. Pat. No. 3,677,245 which discloses a self-contained disposable syringe including a syringe barrel with an open rear end and a needle mounted on the forward end. The needle has a passage therethrough which communicates with the interior of the barrel. A plunger is positioned within the syringe barrel and is movable with respect to the barrel.
U.S. Pat. No. 2,888,923 which describes a syringe for use with a sterile needle comprising a casing and a piston slidably engaged with said casing. The piston comprises a first hollow tube and a second hollow tube within and threadably engaging the first hollow tube. The second hollow tube is axially adjustable with respect to the first hollow tube and adapted for substantially complete insertion therein, whereby the piston length maybe controlled.
U.S. Pat. No. 3,584,626 which discloses a hypodermic syringe having a syringe body, a piston rod arranged movably in the body and an injection needle, in which the injection needle is housed inside the syringe body prior to the use of the syringe. When the needle is moved into its injection position, it is brought into a sealing abutment with a seating member arranged in the syringe body.
U.S. Pat. No. 4,316,463 which discloses a hypodermic injection device wherein the needle is initially isolated from a possibly corrosive medicament, but wherein the needle is movable to a position in flow communication with the medicament only at the moment of injection.
U.S. Pat. No. 4,969,877 discloses a syringe assembly which includes an outer casing within which an inner chamber slides. A plunger having a sealing plug at one end extends into both the inner chamber and outer casing such that the sealing plug is fixedly secured within the interior of the inner chamber and outer casing, yet is free to slide along the length of the inner chamber. The inner chamber and outer casings are structured such that the needle can be retracted completely within the interior of the outer casing when the inner chamber is releasably locked at the rear end of the outer casing. The needle can also be placed into an operational position when the inner chamber with attached needle is releasably locked at the forefront of the outer casing.
U.S. Pat. No. 4,915,699 describes a syringe assembly which includes an outer casing within which an inner chamber slides. A plunger having a sealing plug at one end extends into both the inner chamber and outer casing such that the sealing plug is fixedly secured within the interior of the inner chamber and outer casing, yet free to slide along the length of the inner chamber. The inner chamber and outer casing are structured such that the needle can be retracted completely within the interior of the outer casing when the inner chamber is releasably locked at the rear end of the outer casing.